1. Field of the Invention
The present invention relates to an airbag cushion structure, particularly a structure of an inner vent hole that is formed to allow an inflation gas to flow into a plurality of chambers formed in an airbag cushion.
2. Description of Related Art
Items generally included in an airbag equipped in a vehicle are divided into, first, passenger collision energy absorption performance and, second, safe inflation performance.
The passenger collision energy absorption performance is the ability of an airbag cushion to absorb the passenger's kinetic energy in a vehicle collision, in which the amount of absorbed energy depends on whether the passenger fastens the seat belt, or the vehicle's collision velocity.
Further, the safe inflation performance is to minimize the impact energy applied to a passenger from the airbag cushion that inflates, in which the performance depends on the pressure of an inflator and the size of a vent hole of the airbag cushion.
FIG. 1 shows an airbag cushion 504 with a base chamber 500 and a chest chamber 502 that has inflated. By way of example, the relationships of a vent hole of airbag cushion 504 with the passenger collision energy absorption performance and the safe inflation performance are described as follows.
The passenger collision energy absorption performance largely depends on the size of an outer vent hole 506 formed through airbag cushion 504, when both base chamber 500 and chest chamber 502 inflate.
In this example, that is, both base chamber 500 and chest chamber 502 are under the pressure of the inflation gas, such that an inner vent hole 508 through which the chambers communicate with each other cannot function as a vent hole that allows the inflation gas flow.
On the other hand, when only base chamber 500 is provided, outer vent hole 506 and inner vent hole 508 are both available and the passenger collision energy absorption performance and the safe inflation performance depend on the sizes of the two both holes.
That is, when the sizes of outer vent hole 506 and inner vent hole 508 are large, the safe inflation performance increases whereas the passenger collision energy absorption decreases.
Therefore, determining the sizes of the vent holes of airbag cushion 504 involves a contradiction: the need to increase the vent holes for the passenger collision energy absorption performance or to decrease the vent holes for the safe inflation performance.
However, outer vent hole 506 is an important factor when base chamber 500 and chest chamber 502 are both provided and inner vent hole 508 is influential when only base chamber 500 is provided. As a result, it should be needed to decrease inner vent hole 508 for the passenger collision energy absorption performance and increase inner vent hole 508 for safe inflation performance of the airbag.
The information disclosed in this Background of the Invention section is only for enhancement of understanding of the general background of the invention and should not be taken as an acknowledgement or any form of suggestion that this information forms the prior art already known to a person skilled in the art.